1. Field
One or more embodiments described herein relate to a display device and driving method thereof.
2. Description of the Related Art
A liquid crystal display includes has a plurality of pixels, each including a liquid crystal layer between a pixel electrode and a common electrode. The pixel electrodes are arranged in a matrix form and are connected to switching elements, such as a thin film transistor (TFT). The common electrode is formed over the entire surface of a display panel and is applied with a common voltage. In one circuit configuration, the pixel electrode, common electrode, and liquid crystal layer form a liquid crystal capacitor.
In such a display, a DC voltage is applied to the pixel and common electrodes to generate an electric field in the liquid crystal layer. Light of a certain amount is transmitted through the liquid crystal layer by controlling intensity of the electric field to obtain a desired image.
When the liquid crystal display is driven for a long period of time, or an electric field in one direction is applied to the liquid crystal layer for a long period of time, the electric field is biased to a higher side or lower side based on the common voltage and ions are stuck on an alignment layer of the pixel electrode. As a result, a kind of residual DC voltage exists between the pixel electrode and alignment layer.
When a voltage having polarity opposite to the common voltage is applied, the residual DC voltage weakens the electric field in the liquid crystal. When a voltage having the same polarity as the common voltage is applied, the residual DC voltage strengthens the electric field in the liquid crystal. Therefore, a gray imbalance of the liquid crystal display occurs, which is displayed as an afterimage.